<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<style>
    .clearfix::after{
        content: '';
        display: block;
        clear: both;
    }
    .main .main-left{
        overflow: hidden;
        height: 400px;
        background: red;
    }

    .main .main-right{
        float: right;
        width: 200px;
        height: 200px;
        background: green;
        margin-left: 10px;
    }

</style>
<body>
    <div class="main clearfix">
            <div class="main-right">

                </div>
        <div class="main-left">

        </div>
        
    </div>
</body>
</html>